Primary purpose of Section 302 notification requirements

What is the primary purpose of Section 302 notification requirements?  

Notifications indicating that a facility has one or more extremely hazardous substances in excess of the threshold planning quantity help to identify locations within the State where emergency planning activities can be initially focused.  While the substances on the list do not represent the entire range of hazardous chemicals used in commerce, they have been designated as those substances which are, in the event of an accident, most likely to inflict serious injury or death upon a single, short-term exposure.  Therefore, Section 302 notifications should be useful in helping State and local governments identify those areas and facilities that represent a potential for experiencing a significant hazardous material incident.